VIZIO VT420M Power up issue

[CSF]

If the tv is cold and has been unplugged for several days it will power up fine, but after a short time goes down to backlights only. The VIZIO front light stays bright. The power board and the regulator on the main board test good. I took a can of dust spray and I knew if it was upside down it would putout cold propane gas. I tried cooling down some components. In the picture see the heat sink on the far left side of the board cover with metal with holes in it. I marked it with a yellow arrow. When I cooled that part down the set came right on. Does anyone know what the function of that component is and what I might do to correct the problem? Re-solder perhaps? I have not found an drawing of that board so it is hard to know where to go from here. The board number is CBPF9D1KZ4. BTY this forum is fantastic!

[budm]

Re: VIZIO VT420M Power up issue

You will have to remove that shield to see what are in side that section.

[Nick's Tvs]

Re: VIZIO VT420M Power up issue

Seems to me a reflow of the BGA chip or a rework will do the trick.

[CSF]

Re: VIZIO VT420M Power up issue

Okay I decided to take the metal cover off and heated the heat sink to melt the glue holding it on. So this is the processor in fact it says AMD on it so it must be. From the top I don't see any soldered connections. I see connections on the underside of the board. How should I go about reflowing the connections?

[CSF]

Re: VIZIO VT420M Power up issue

I suppose the only thing that makes sense is reflowing from the bottom directly below the AMD chip.
Is the hot glue a special type that holds the heat sink on?

[CSF]

Re: VIZIO VT420M Power up issue

I tried reflow on the back of the board or the underside of the suspect chip. It did not work. Looking at the top of the chip where the part number are there are no visible soldered connections. That's why I heated the other side for reflow. It was when I super cooled the heatsink that tv set came on normally. Cloud it be the chip that is bad?

[dskall]

Re: VIZIO VT420M Power up issue

What components are around the chip?

[CSF]

Re: VIZIO VT420M Power up issue

There is a ram or memory chip beside the processor chip and they both have heat sink on them.

[CSF]

Re: VIZIO VT420M Power up issue

After heating to reflow the problem is constant now. Even freezing it won't make it work. Even if I could buy a new AMD chip I don't have a clue how to install it.

[CSF]

Re: VIZIO VT420M Power up issue

The chip that needs reflowed look like the one in this picture. Anyone have experience with this?

[CSF]

Re: VIZIO VT420M Power up issue

I found a process for DIY reflowing here on the forum. Remanufactured main boards for this are $125 plus shipping and no one has replacements in stock. Ebay has none either. $125 is more than the set is worth, so I'll give this a shot. When I heated the underside I only I think it got just hot enough to make it worse. This process will evenly heat top and bottom to a predetermined temp.


https://www.badcaps.net/forum/showthread.php?t=36740

[CSF]

Re: VIZIO VT420M Power up issue

The reflow per the instructions didn't work. I used an infrared thermometer for control. I guessing the chip is what is bad. I'll be looking for a reasonably priced main board. Although $123 isn't bad for a 1080P HD TV is it?

[budm]

Re: VIZIO VT420M Power up issue

That is a lot of money for main board for 42" 2010 TV.